Hi Jon!
I'm currently running a small board as well, but we're bandwidth intensive. Right now I'm eating a good 100gb a month (and that's with sharing loads with other affiliates

) and we're an extremely young podcast (5 episodes). Anyhow, we'll be transitioning to a dedicated server this summer and that is where your best bet lies.
As boards grow so will your demands. Eventually, a shared hosting plan won't provide enought. You'll need to make the move to a dedi.
Currently I use
Surpass Hosting and they're doing a dang good job. When I make the "big move" it will be to one of their managed dedicated servers.
At a good deal too. Expect a good $100ish dollards for a lowish-end dedicated

. Obviously that price rises with what exactly you get.